A complex fluid machine (a fluid pump having an expansion device) is known in the art, as disclosed in Japanese Patent Publication No. 2004-108220, which is applied to a bottoming cycle (Rankine cycle) power generating system. In such a conventional fluid machine, a turbo pump (fluid pump) for pressurizing liquid phase working fluid, a turbine (expansion device) coaxially connected to the turbo pump for expanding gas phase working fluid which is heated by a heat exchanger, and an electric power generator coaxially connected to the turbo pump for generating the electric power, are integrally formed into one unit, wherein the turbo pump and the electric power generator are driven by rotational force produced by the operation of the turbine.
Although it is disclosed in the above complex fluid machine, that the fluid pump, the expansion device and the electric power generator are integrally formed into one unit, heat transfer of the working fluid flowing in the fluid pump and the expansion device is not considered.
Namely, when the heat of the working fluid at an outlet side of the expansion device is transferred to the working fluid at an inlet side of the fluid pump, the working fluid flowing into the fluid pump is likely to be boiled. When the boiling of the working fluid occurs, the working fluid includes gas phase fluid therein (generation of cavitation), so that volume efficiency of the fluid pump will be decreased.
On the other hand, it is considered to more efficiently operate the Rankine cycle, by transferring the heat of the working fluid at the outlet side of the expansion device (the waste heat remaining in the working fluid even after the expansion) to the working fluid in a heating side (at an outlet side of the fluid pump, at a heating device), so that an amount of super heat for the working fluid is further increased.